The aim of the study was to assess the effect of effective microorganisms on selected parameters of the cellular immune response in the colostrum and milk of sows and in the serum of suckling piglets. A total of 60 female crossbred sows and 60 female piglets were used in the experiment. The material for analysis comprised colostrum and milk collected from sows and blood samples from piglets. Immune response parameters were determined by flow cytometry and ELISA kits. The results showed high expression of CD4-CD25-FoxP3, CD4, and CD25 in the colostrum and milk of sows and of CD4, CD8 in piglet blood. The use of EM Bokashi® as a feed supplement for sows during colostrogenesis stimulates cellular immune mechanisms, expressed by an increase in the Treg cell population in the colostrum and milk, which contributes to effective elimination of microorganisms in the first period of piglets’ life.